From: nagle@netcom.com (John Nagle) Subject: Re: HOME-BREW: Cheap accelerometer input devices Date: Fri, 25 Apr 1997 03:56:19 GMT Message-ID: Organization: Netcom On-Line Services Robin Hollands writes: >Michael J. Sinclair wrote: >> For you home-brewers out there, there are a number of relatively >> inexpensive (and untapped) markerless tracking sensors ready to be >> incorporated. We use both linear and rotational (gyro) accelerometers >> for position and attitude tracking. >> >> Check out Crossbow's 1, 2, or 3 linear accelerometers (compliments of >> the auto air-bag industry) at >> >> www.xbow.com >Since accelerometer based devices offer the promise of truely >limitless tracking, its perhaps surprising that no-one is commercially >producing a tracker based on them. The truth is that although >rotational gyroscopes are usuable for orientation tracking (although >they still suffer from drift to varying degrees), the use of linear >accelerometers is extremely difficult. Well, there's the GyroMouse, but it is crude. Low-range accelerometers exist; the Analog Devices ADXL05 is an example. The ADXL series are particularly interesting in that they go down to DC, which most low-cost accelerometers do not. So you can see gravity. But integrating twice to get position is too drift-prone for much use. Low-end rate gyros are good for maybe 2 deg/min, which is good enough for many purposes. For algorithms, read the book "Modern Inertial Technology". John Nagle nagle@netcom.com (John Nagle)